EFFECT OF IRRADIATION WITH PULSED ION BEAM ON THE MICROSTRUCTURE OF TiH 2

Abstract

Titanium has long been of interest as hydrogen storage material since titanium has a high affinity to hydrogen isotopes. Titanium deuteride or tritide is an important nuclear material used in the field of nuclear technology. Investigations concerning hydrogen–titanium system seem to mainly focus on the hydrogen thermal desorption spectra so as to study hydrogen desorption kinetics from metal hydride and to determine the rate–controlling step, but little is known on the evolution of its compositional changes under a much more un–equilibrium condition. In the past two decades, the intense pulsed ion beam (IPIB) technique has received extensive attention as a tool for surface modification of materials. Compared with conventional ion implantation, IPIB irradiation into materials possesses a higher energy density with shorter pulse width and be typical of more intense thermal–mechanical effect. From such a point of view, considering the features of extreme high heating and cooling rate of IPIB, IPIB as a method to evaluate the stability characteristics of titanium hydride film is utilized in order to determine a predictable behavior of the film’s evolution under an extreme un–equilibrium external condition. In current study, TiH2 films irradiated by intense pulsed ion beam have been investigated by using scanning electronic microscopy, surface profilometer, X–ray diffraction and slow positron annihilation, in order to evaluate the effect of irradiation with pulsed ion beam on the microstructure of TiH2. Three sets of TiH2 films are irradiated several shots * D} <2bj ^SG 11205136 mlL-C : 2013–03–18, ml['-C : 2013–07–20 j3 : ℄ n, , 1987 W, %e DOI: 10.3724/SP.J.1037.2013.00122 1270 p ` AE x 49 * at energy density ranging from 0.1 J/cm to 0.5 J/cm. No noticeable phenomenon of melting and change of phase structures have occurred to samples under irradiation of 0.1—0.3 J/cm. However, phenomenon of melting and indication of cracking has been detected on the surface after energy density reaches 0.5 J/cm. Besides, desorption of hydrogen from the film, and a titanium hydride with a body centered tetragonal structure (bct), seldom reported by researchers and formed under extreme conditions, has also been identified only after energy density of IPIB reaches 0.5 J/cm. S parameter of slow positron annihilation reflects that the crystal defect structures have been greatly changed by IPIB irradiation, in which S parameter reaches a large value at 0.3 J/cm with 1 shot, while a small one at 0.5 J/cm with 5 shots.